XML stands for Extensible Markup Language. It is different and in some ways better than HTML which stands for HyperText Markup Language.
Extensible- XML is extensible. It lets you define your own tags.
Markup - The most attractive feature of XML has to be its ability to allow its user to create their own tags. The tags that can be created will be similar to tags in HTML. But with XML you are afforded the opportunity to define your own tags.
Language - XML is a language that is very similar to HTML. But it’s much more flexible because it allows to create custom tags. In this way XML acts like a meta-language: a language that allows us to create or define other languages. For example, with XML we can create other languages, such as RSS.
HTML can be called a presentation language, whereas XML is more of a data-description language. XML unlike HTML isn’t just suited to the Web – it can be used in a variety of different contexts. For example, Web Services may make use of XML to send requests and responses back and forth.